What Is DNS? How It Works and Why It Affects Speed

DNS explained simply: how a DNS server turns a site name into an IP address, why slow DNS makes pages lag, and how to switch to a faster one.

September 1, 2026

DNS is the system that translates a website's name into the numbers a computer understands. Think of it as the internet's phone book: instead of people's names it lists website names, and instead of phone numbers it lists IP addresses. Without it, you would have to remember a string like 172.217.16.142 for every site, and how fast DNS answers affects how quickly a page opens.

What is DNS in simple terms?

When you type a web address into your browser, the computer can't do anything with the name itself. Websites are found by numeric IP addresses, not by names. DNS (Domain Name System) is a huge distributed database that stores the "site name → IP address" pairs and returns the right record in a fraction of a second.

Compare it to a phone book. You remember a person's name, not their number, so the book supplies the number for you. Your browser remembers the site's name, and DNS supplies the address of the server where the site actually lives.

One important detail: the database isn't stored in one place. If it all lived on a single machine, that machine wouldn't last a minute. Instead, records are spread across thousands of servers worldwide. At the top of the hierarchy are the root servers: 13 logical addresses, each backed by hundreds of physical machines.

How does a DNS server work?

Every time you open a new page, a DNS lookup happens. Here is what it looks like:

• Your browser first checks its own cache and the hosts file on your computer, in case the address is already known.
• If nothing is found, the request goes to a DNS server. By default, that's your ISP's server.
• The server checks its cache. If the record is there and hasn't expired, the answer comes back right away.
• If not, the server works through the chain itself: it asks a root server, then the server for the top-level domain (such as .com), then the server responsible for the specific domain.
• The IP address it finds is returned to your browser and cached for as long as the site owner allows (a setting called TTL, usually from a few minutes to a day).
• Only then does the browser connect to the site and start loading the page.

The whole chain usually takes 20–120 milliseconds, and just a few when the answer comes from a cache. That time is what makes a site feel "instant" or "laggy."

What is a DNS server and why do you need one?

A DNS server is a computer that takes the question "what's the IP address for this name?" and returns the answer. It matters for three reasons:

• Convenience. A name is much easier to remember than a number.
• Flexibility. A site owner can move to another server or change the IP, and you don't have to reconfigure anything. DNS simply hands out the new address.
• Load balancing. One domain can be served from several machines at once, and DNS can point you to the closest or least busy one.

For most people DNS is configured automatically, and nobody asks them to think about it. But you can change it, as we'll see below.

Why does slow DNS make the whole internet feel slow?

A DNS lookup is the first step before any page loads. If it's slow, the delay is added to every link you click and to every image or script requested from another domain. A single page can make dozens of such requests.

Three common causes:

• Your ISP's DNS server is overloaded. At peak hours it answers with a delay. This is one of the hidden reasons sites lag specifically in the evening. For more, see why video buffers only in the evening.
• The server is geographically far away. The greater the distance, the longer the signal takes to travel there and back.
• Stale cache and glitches along the chain. One slow node slows the entire process.

Which public DNS server should you choose?

Instead of your ISP's server, you can use a public one. These are open services that usually respond faster and more reliably.

Switching takes a couple of minutes. One limitation is worth knowing up front: a DNS server can see which domains you visit, even though it can't see the contents of the pages. What else your ISP knows about you is covered in what your ISP can see, where DNS queries get their own section.

How can you test and speed up your DNS?

To tell whether DNS is the slow part or something else is:

• Open a site that usually loads slowly and note the delay before the first content appears.
• Switch to a public DNS and open the same site, ideally after restarting your router or device.
• If the page now starts loading noticeably faster in the first few seconds, DNS was the problem.
• If there's no difference, the issue is your connection or the load on your device.

How to change DNS manually:

• Windows: network settings → adapter properties → IPv4 protocol → enter the addresses manually.
• macOS: network settings → DNS → add the server addresses.
• Smartphone: in your Wi-Fi network's settings, usually in the same place as the IP address and gateway.
• Router: the WAN or DHCP section. The new DNS then applies to every device at home right away.

If you don't want to set up each device separately, do it once on the router. The general approach is described in how to set up a secure connection on all your devices.

When is DNS not the problem?

If a site is slow to load content (images, video, scripts) after the page has already opened, DNS isn't to blame. It did its part in the first few milliseconds. The cause is usually your connection, the load on the site's server, or congestion on your ISP's network.

Open Wi-Fi in cafés and airports is a separate story. A badly configured DNS there can become a security risk, because DNS queries are an easy way to tamper with traffic. For what to check before you connect, see public Wi-Fi security. And if you already use a secure connection, make sure your requests aren't going around it: how to check for IP and DNS leaks.

FAQ

What is DNS in simple terms?

It's the internet's phone book. You type a site's name, and DNS finds its numeric IP address, which your browser then connects to.

What is a DNS server for?

It answers the question "what's the IP address for this name?" and keeps the answers in a cache. Thanks to it, you don't have to remember numbers, and site owners can change servers without you noticing.

How does a DNS lookup work?

Your browser checks its own cache, then asks a DNS server. The server answers from its cache or works through a chain of servers to reach the right domain. It usually takes 20–120 ms.

What's the difference between DNS and an IP address?

An IP address is the server's real "number," for example 172.217.16.142. DNS is the system that links a readable name to it. A domain can change its IP while the name stays the same.

What happens if DNS doesn't respond?

The site won't open even though your internet works, and you'll see an error like "server IP address could not be found." Switching to a public DNS or restarting your router usually helps.

The short version

DNS is an invisible but essential step before any page loads: it turns a site's name into its real address. A slow DNS server adds delay to every click, and switching to a public one is one of the easiest ways to speed up page loading without changing your ISP. If you need one secure connection across several devices, the options are laid out on the pricing page.